I think it's an interesting one but I've read a couple of books about a similar topic - "Pre-suasion" by Robert Cialdini being a good one. The book is about factors that influence decision making and think there is a lot of cross-over, well worth a read but will try and summarise what I remember from the book in relation to your post.

Humans are basically hard wired to look for patterns in things and when we see or experience personality traits then we can group them in to a certain set of stereotypes. The reason we look for patterns is because it requires a lot less energy for the brain to process and, effectively, the brain takes short cuts to process things.

This is why people are quick to judge because it is usually based on a pattern they have either experienced, seen or been told about (e.g. parents/society telling you "x is bad, don't listen to them").

I agree that there is an element of projecting your own thoughts and feelings out there to the world but that can also be because you've had a "moment" before that incident has happened causing you to judge (e.g. argument with your partner putting you in a bad mood for the day therefore everyone is a @@!"£%).

And I would like to add to your definition of character as well, which I read from another book called "Story: Substance, Structure, Style, and the Principles of Screenwriting by Robert McKee and it goes something like this - "A persons true character is a set of personality traits that are only revealed when they face extreme pressure".

Food for thought anyway!